imcontrast

Syntax

Description

Use the imcontrast function to create an Adjust Contrast
tool. The Adjust Contrast tool is an interactive contrast and brightness adjustment tool
that you can use to adjust the black-to-white mapping used to display a grayscale image.
For more information about using the tool, see Tips.

Examples

Adjust the Contrast of the Current Image

Read an image into the workspace. Adjust the contrast of the
current image.

imshow('pout.tif')
imcontrast

Adjust Image Contrast, Specifying Figure Handle

Read an image into the workspace and define the handle of the
figure as h1. Open a second figure window and define the
handle of that figure as h2. Adjust the contrast of the first
figure by specifying h1 in the call to
imcontrast.

Output Arguments

htool — Handle to Adjust Contrast tool figurehandle

Handle to Adjust Contrast tool figure, returned as a handle.

Tips

The Adjust Contrast tool presents a scaled histogram of pixel values (overly
represented pixel values are truncated for clarity). Dragging on the left red bar in the
histogram display changes the minimum value. The minimum value, and any pixel value less
than the minimum, display as black. Dragging on the right red bar in the histogram
changes the maximum value. The maximum value, and any value greater than the maximum,
display as white. Values in between the red bars display as intermediate shades of
gray.

Together the minimum and maximum values create a "window". Stretching the window
reduces contrast. Shrinking the window increases contrast. Changing the center of the
window changes the brightness of the image. It is possible to manually enter the
minimum, maximum, width, and center values for the window. Changing one value
automatically updates the other values and the image.

Click and drag the mouse within the target image to interactively change the
window values. Dragging the mouse horizontally from left to right changes the
window width (i.e., contrast). Dragging the mouse vertically up and down changes
the window center (i.e., brightness). Holding down the Ctrl key before clicking and dragging the mouse accelerates the
rate of change; holding down the Shift key
before clicking and dragging the mouse slows the rate of change. Keys must be
pressed before clicking and dragging.

When you use the tool, imcontrast adjusts the contrast of
the displayed image by modifying the axes CLim property. To
modify the actual pixel values in the target image, click the Adjust
Data button. This button is unavailable until you make a change
to the contrast of the image.

The Adjust Contrast tool can handle grayscale images of class
double and single with data ranges
beyond the default display range, which is [01]. For these images, imcontrast sets the
histogram limits to fit the image data range, with padding at the upper and
lower bounds.

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